Glycolysis is an important pathway in almost all cells. Our studies of its biochemical genetics in Escherichia coli, and in the yeast Saccharomyces cerevisiae, are directed to problems of gene expression and in vivo function. This proposal is for support of enzymological work deriving from the mutant studies. The main project concerns several genes and phosphofructokinase activities in E. coli; another project is to clarify the relationship between several yeast hexokinase isoenzymes.